[bsza]

Maybe it was such an honorable craft that people were more likely to name themselves after it compared to other trades?

[mackinley]

I have that surname but not for the reason that a blacksmith was in my family. My great grandparents took the name Smith at Ellis Island to Americanize themselves. I suspect this backstory is probably quite common in the US, especially amongst Irish and Italian immigrants in the late 18 to early 1900's.